1. Field of the Invention
The present invention relates to helicopters generally and, more particularly, but not by way of limitation, to a novel tail rotor assembly for helicopters which provides substantially improved performance over conventional tail rotors.
2. Background Art
Although there are some alternative designs, helicopters are conventionally constructed with a single main rotor blade. A condition associated with the single main rotor arrangement is that the main rotor generates a horizontal torque component which must be offset. To accomplish this, conventional helicopters, both model and full-scale, employ a single vertical tail rotor mounted on either the left or the right side of the distal end of the tail boom. A tail rotor is generally considered to be the weakest feature of a conventional helicopter in terms of control and performance.
When the helicopter is trimmed for "hands off" hover in forward flight, the tail rotor creates an asymmetrical drag. If the tail rotor is mounted on the left side of the tail boom, the drag causes a left yaw condition which tends to rotate the helicopter counterclockwise. If the tail rotor is mounted on the right side of the tail, a right yaw condition exists.
Also, in forward flight, as air speed changes, if there has been a trim adjustment of the tail rotor for a left or right yaw condition at one speed, the required trim adjustment changes as forward speed changes. Similar adjustments are required for changes in wind velocity and direction to maintain stability of the helicopter.
Most modern helicopters use a vertical fin to augment the directional stability of the tail rotor and, for greatest effectiveness, these two components should both be located at the end of the tail boom. Both near and far relative locations of these two components have disadvantages, so the final design must be a compromise. Additionally, since the rotor will either blow air at the fin or suck air past it, there is a resultant power penalty.
A further problem with conventional tail rotors, particularly with smaller helicopters, is that the rotor presents a safety problem to personnel on the ground and also presents a ground clearance problem. Ground clearance is particularly a problem when landing on unprepared ground, since the usual rotational direction of the top blade on the tail rotor going back can cause the rotor to bat rocks at the fuselage.
Accordingly, it is a principal object of the present invention to provide a tail rotor assembly for a helicopter that eliminates undesired yaw conditions.
It is a further object of the invention to provide such a tail rotor that permits improved control of the helicopter in a variety of conditions.
It is an additional object of the invention to provide such a tail rotor that reduces personnel safety and ground clearance problems.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.